The heart is the center of human circulatory system that pumps blood through our body. It is a muscle that pumps the blood only in one direction. In order for the heart to effectively keep this unidirectional flow of blood, it must have properly functional valves that prevent back flow through its system, or regurgitation. The heart is divided into four chambers, right and left atria, and right and left ventricles. The four chambers are connected to the aorta, the inferior and superior vena cavas, the pulmonary artery, and the pulmonary veins.
The mitral valve (“MV”) separates the left atrium from the left ventricle while the tricuspid valve (TV) separates the right atrium from the right ventricle. The aortic valve (“AV”) is located between the left ventricle and the aorta while the pulmonary valve (“PV”) is located between the right ventricle and the pulmonary artery.
Generally, valves should open and close completely with every heart beat or contraction. Incomplete opening and closing of the valves cause improper flow of blood. Valvular diseases are divided into two categories, regurgitation and stenosis. Regurgitation is a failure of valve to close completely and stenosis is a failure of valve to open completely.
Mitral valve regurgitation (“MVR”) is a common cardiac valve disorder that is caused by an incomplete closure of the MV. The MV is located between the left atrium and the left ventricle. Over time, MVR burdens the heart and worsens its ability to pump blood properly. Such stress on the heart will ultimately lead to a heart failure.
Traditional treatment of a worsening MVR requires an open heart surgery with sternotomy or thoracotomy with cardiac arrest and cardiopulmonary bypass. Once the chest is open and access to the heart is gained, the MV is either repaired or replaced using an artificial valve.
Although very effective, this open-heart procedure is a high risk surgery accompanied by substantial morbidity and prolonged convalescence. The mortality due to the surgery itself can be as high as 5%. As a result, the procedure often is not offered to patients who are insufficiently symptomatic to justify the surgical risk and morbidity, or to patients with substantial co-morbidity. It is reserved only for those with severe symptomatic MVR.
This high morbidity rate of an open heart surgery has motivated further research to develop a safer and less risky alternatives to repair an MVR. Much of the research involves the use of cardiac catheterization.
Recently, this inventor presented a thesis regarding “mitral valve cerclage coronary sinus annuloplasty (MVA)” showing outstanding result of an MVR treatment through applying circular pressure around the mitral annulus. This thesis has been filed through PCT as an international patent application and published with its publication number WO2008/060553, which is incorporated herein in its entirety.
The aforementioned thesis and published patent application disclosed the mitral cerclage coronary annuloplasty (“MVA”) procedure. Briefly explained, a catheter is placed at the coronary sinus after accessing the right atrium through the jugular vein, and then a cerclage suture is passed through the proximal septal vein.
This cerclage suture can easily pass through the right ventricular outflow tract (“RVOT”), and this inventor defines this technique as “the simple mitral cerclage annuloplasty.” Then the cerclage suture can be easily pulled into the right atrium thus placing the cerclage suture circumferentially around the mitral annulus.
Once positioned, tension is applied to the cerclage suture and tightens the mitral valve. This brings together the two leaflets of the MV, so that they are approximated and reduce the size of its incomplete closure. This theory can obtain a very similar result when compared to the results of a conventional surgery that directly tightens the mitral annulus, and show immediate reduction of an MVR.
However, there are several technical problems to be solved. First, there is a need to have a tension locking device to be able to apply proper tension to the cerclage suture and maintain the tension.
According to the aforementioned research result, approximately 400-1200 g tension is needed to have a good treatment result. In addition, individualized tension must be applied constantly until the point where the mitral regurgitation is reduced, then, the suture needs to be fixed at that point, so that the same tension is maintained. Further, this tension must be sustained regardless of its constant resistance from every beat of each heart contraction.
Since this tension is maintained with a very fine cerclage suture (i.e., 0.014 nylon cerclage used in the researches), it can cause damages on the neighboring cardiac tissues where the suture contacts and exerts its pressure. Especially, since the cerclage wraps around the tricuspid valve (TV), it could affect the function of the TV and damage the valve itself and its appendages. This invention is intended to provide viable solutions to overcome these problems.